Such flap devices serve, for example, as exhaust gas accumulation flaps or as exhaust gas recirculation flaps in the exhaust gas system of an internal combustion engine. Exhaust gas contains pollutants that must not escape to the outside, so that a reliable sealing must be provided along the shaft that protrudes outward to an actuator. This sealing must function perfectly at all times under varying thermal loads. A precise controllability must also be achieved with the flaps in order to meet the emission regulations for modern internal combustion engines.
Various flap devices have previously been described which attempt to satisfy these objectives. DE 20 2008 005 992 U1 describes a flap valve which is supported on two sides and which is intended for use in the hot area of exhaust systems. A seal is arranged on an inclined shoulder of the shaft being pressed by a spring force against an opposite sealing surface of the housing. The sealing point also serves to axially secure the flap shaft. The centering of the flaps in the channel and an occurring thermal expansion may lead to a jamming of the flap in the channel when the flap is closed.
An exhaust flap is also described in JP 07259586, wherein a thin metal ring fixed with screws is arranged behind the bearing bush, the outer circumference of the ring resting on the laterally delimiting wall of the surrounding housing. The metal ring is displaced along the surrounding side wall when a thermal expansion occurs. Due to the small contact surface or to scores formed in the housing over time, no sufficient tightness can be provided over the long term. Increased wear is also caused by the turning of the metal ring.
The prior art designs are disadvantageous because they fail to provide sufficient sealing if thermal conditions change and also fail to provide an adjustability of the flap without a risk of jamming.